New NASA images reveal an alarming crack in the middle of a Greenland glacier

New NASA photos have revealed an unusual crack forming across Greenland's Petermann Glacier, threatening to release a huge iceberg into the Arctic Sea. Worryingly, scientists aren't sure how the rift formed in the first place, or what it'll do next.

While cracks aren't an uncommon sight in ice sheets around the globe these days, this new discovery is alarming because it's formed in the middle of one of Greenland's glaciers, not at its edges, and it's not something scientists saw coming.

In fact, NASA scientists were first notified of the rift on Twitter last week, by Dutch scientist Stef Lhermitte from Delft University of Technology.

Lhermitte studies satellite remote sensing and recently stumbled across an image of what appeared to be a giant crack forming in the Petermann Glacier.

What's especially worrying is that the new rift has formed near the center of the glacier's floating ice shelf.

This isn't where scientists expect to find new rifts - usually the cracks begin to form along the edges of a glacier, where the ice melts.

"Amazing to see a new crack forming and in a location well upstream of the present day calving front," Jason Box, a professor with the Geological Survey of Denmark and Greenland, who wasn't involved in the latest study, told Chris Mooney from The Washington Post.

That's because, generally speaking, the farther inland a crack forms, the more unstable it makes the glacier, as CNN reports.

Glacier ice shelves act as a buffer between the inland glacier and the open ocean - the less of a buffer there is, the quicker the land ice of the glacier is going to melt.

And with the Petermann Glacier holding back an estimated 30 centimetres (1 foot) of sea level rise, that's a pretty big deal.

Without further research, no one's quite sure how the rift started, but Eric Rignot, an earth scientist from NASA and the University of California at Irvine, told Mooney that the unusual crack could "indicate that the ice shelf has gotten too thin in the middle".

But the good news is the new rift seems to getting close to a 'medial flowline', which is a flow of ice in the middle of the ice shelf that might slow the crack down somewhat and "exert a stagnating effect on the propagation of the new rift toward the older one," Operation IceBridge wrote on Facebook.

At this point, no one's sure how the crack will progress, but one thing's for certain, researchers are going to be keeping a close eye on it.